1. Field of the Invention
This invention relates to a method and apparatus for filtration cleaning of air ducts that are used in systems for interior heating, ventilating, and/or cooling of buildings.
2. Related Prior Art
Many modern residential, commercial, and industrial buildings have indoor air control systems for heating, ventilation, and cooling (HVAC) that recirculate air through extensive ducts which over time become laden with particulates of dust, fibers, pathogens, fungi, debris and the like creating a health hazard to the occupants. Periodic cleaning of the ducts is required for the health of the occupants and for efficient air system operation.
Portable motor vehicle mounted vacuum cleaning apparatus operates from the exterior of buildings and thus suffers in accessibility to the ducts in large and multiple story buildings. Cleaning efficiency suffers due to the long flexible hose or duct required to connect to the HVAC system ducts. Exhausted air is discharged into the atmosphere (U.S. Pat. 5,030,259). Vacuum cleaning apparatus for installation and operation from within buildings require assembly of modular units, sized for passage through doorways. In addition to the vacuum blower unit, one or more filter units including a high efficiency particulate air (HEPA) filter are required in that exhausted air of the apparatus is discharged into the interior environment of the building. Compressed air nozzles are introduced into the ducts as an effort to loosen contaminating materials from the inner surfaces of the ducts (U.S. Pat. Nos. 4,968,333 and 5,069,691). Effective vacuum cleaning suffers due to low capacity of the blowers and due to inefficient loosening of the contaminating materials adhered to the duct surfaces.